The compressor of the type considered herein, used in refrigeration systems and driven by a linear electric motor, comprises a housing, usually hermetic and lodging a non-resonant assembly, including a crankcase. In this type of known construction, the crankcase incorporates a cylinder inside which is defined a compression chamber, having an end usually closed by a valve plate and by a head, and an um open opposite end through which is assembled a piston, reciprocating inside the cylinder and defining, therewith and with the valve plate, the compression chamber.
The piston used in the subject compressor presents a cylindrical tubular body, with an open rear end and a front end closed by a top wall which carries a suction valve. The cylindrical tubular body defines a tubular skirt portion of the piston, which is closed, next to an end edge, by the top wall (defining a head portion in the piston). For these constructions, the top wall of the piston presents suction openings selectively closed by the suction valve, as described and illustrated in the Brazilian patent document PI 1000181-6.
The piston is coupled, usually by means of a rod, to an actuating means, which carries magnets driven by the supply of energy to the linear motor mounted to the crankcase.
The rod is provided inside the piston and presents a first end, affixed to the piston, in the top wall region thereof, and a second end affixed to the actuating means.
The linear motor drives the actuating means in a reciprocating motion, being responsible for generating the required thrust for displacing the piston inside the cylinder and for the compression of the refrigerant fluid in the form of gas. The piston, the rod and the actuating means form a movable assembly of the compressor, to which movable assembly is coupled a resonant spring mounted in order to apply opposing axial forces on the piston, upon the reciprocating axial displacement of the latter inside the cylinder. The resonant spring acts as an axial displacement guide for the piston, further acting on the movable assembly of compression, together with the linear motor of the compressor. The movable assembly of compression and the resonant spring define the resonant assembly of the compressor.
In some constructions of linear compressor having the suction being made through the piston, it may be necessary the assembly, in the interior thereof, of a noise muffler (suction muffler), in order to inhibit the transmission, through the gas, of different frequencies generated by the gas flow through the suction valve and by the motion the latter (WO2004/106737, PI1004881).
In the solution PI1004881, the suction muffler is mounted radially spaced inwards from the tubular skirt portion of the piston, defining, in this spacing, a volume for a chamber acting on the noise attenuation, having been designated as chamber C3 on said prior patent application.
Although said suction muffler construction internal to the piston provides efficient noise attenuation, it presents the drawback of allowing the heating of the gas being admitted in the interior of the piston. The chamber continuously holds a volume of gas therein, which receives the heat conducted from the top wall of the piston to its tubular skirt portion, hence to the gas contained inside said chamber and from the latter to the gas being drawn through the piston. The gas heated in said chamber is progressively mixed with the gas entering in the piston, in a common region of the latter adjacent to the gas inlet, heating the gas being sucked to the compression chamber. This undesirable heating of the gas being drawn through the piston tends to cause an efficiency loss which is more relevant than the acoustic gain obtained with the chamber of this prior solution.